Fixed microbit demo

Author: dbrattli

examples/microbit/Build.fs

@@ -1,3 +1,4 @@
+open System.IO
 open Fake.Core
 open Fake.IO
 
@@ -6,27 +7,39 @@ open Helpers
 initializeContext()
 
 let srcPath = Path.getFullName "src"
+let appName = "app.py"
 
 Target.create "Clean" (fun _ ->
     run dotnet "fable-py clean --yes" srcPath // Delete *.py files created by Fable
 )
 
 Target.create "Build" (fun _ ->
     run dotnet $"fable-py -c Release" srcPath
+
+    // Rewrite imports to flat file system.
+    let python = File.ReadAllText($"{srcPath}/{appName}")
+    let python = python.Replace("fable_modules.fable_library.", "")
+    File.WriteAllText($"{srcPath}/{appName}", python)
 )
 
 Target.create "Flash" (fun _ ->
-    run flash "" $"{srcPath}/app.py"
+    run flash appName srcPath
+)
+
+Target.create "FableLibrary" (fun _ ->
+    run ufs $"put util.py" srcPath
 )
 
 open Fake.Core.TargetOperators
 
 let dependencies = [
     "Clean"
         ==> "Build"
-
     "Clean"
+        ==> "Build"
         ==> "Flash"
+    "Clean"
+        ==> "FableLibrary"
 ]
 
 [<EntryPoint>]

examples/microbit/Helpers.fs

@@ -73,6 +73,7 @@ let createProcess exe arg dir =
 
 let dotnet = createProcess "dotnet"
 let flash = createProcess "uflash"
+let ufs = createProcess "ufs"
 
 let npm =
     let npmPath =

examples/microbit/README.md

@@ -2,10 +2,20 @@
 
 Write your F# program in `src/App.fs`.
 
+Note that the Fable Library is not supported so it's very limited what
+you can do. The needed parts of fable library need to be ported to work
+with MicroPython see `util.fs` as an example.
+
+The micro:bit have a flat file-system so all files needs to be in the
+same top-level directory.
+
 ## Install
 
+These tools are needed by the Build script:
+
 ```sh
 pip install uflash
+pip install microfs
 ```
 
 ## Build

examples/microbit/src/App.fs

@@ -2,4 +2,31 @@ module App
 
 open Fable.Python.MicroBit
 
-display.scroll ("Fable Python!") |> ignore
+//display.scroll ("Fable Python!") |> ignore
+
+let mutable time = 0
+let mutable start = 0
+let mutable running = false
+
+while true do
+    if running then
+        display.show (Image.HEART)
+        sleep (300)
+        display.show (Image.HEART_SMALL)
+        sleep (300)
+    else
+        display.show (Image.ASLEEP)
+
+    if button_a.was_pressed () then
+        running <- true
+        start <- running_time ()
+
+    if button_b.was_pressed () then
+        if running then
+            time <- time + running_time () - start
+
+        running <- false
+
+    if pin_logo.is_touched () then
+        if not running then
+            display.scroll (int (time / 1000))